54 THE FROG CHAP, in 



Dogfish). An additional skull should be carefully cleaned, and then 

 boiled until the numerous bones become separated from one another or 

 disarticulated. 



After observing the form and relations of different parts of the 

 skeleton as described on pp. 35 and 36 (Fig. 8, A), they may be sepa- 

 rated from one another for more detailed examination. The individual 

 vertebrae should be strung on a piece of wire or string so as to prevent 

 their being lost or misplaced. 



With the specimen before you, work through the characters of the 

 axial skeleton (pp. 36 46) : if you omit the details given in small type 

 at the present stage, do not forget to examine them subsequently. 

 Make sketches of a. Any one of the vertebrae from the 1st to the 7th, 

 from the side and from the front or back ; b. the ist vertebra ; c. the 

 urostyle ; d. the skull from above and from below ; and e, the 

 hyoid. 



It requires considerable skill to make a satisfactory preparation of the 

 chondrocranium, and it is advisable to examine that of a Dogfish first ; 

 but if you wish to attempt it, procure a large skull which has not been 

 dried, and boil it in water. Carefully separate, by means of a scalpel, 

 most of the investing bones (p. 43) ; the palatines, pterygoids and 

 quadratojugals, and the dentaries and angulosplenials cannot well be 

 disarticulated without destroying the soft cartilaginous parts beneath 

 them. 



Make out I. The brain-case and \\sfontanelles and nerve-apertures 

 2. The olfactory capsules. 3. The auditory capsules. 4. The palato- 

 quadrate bar (to which the palatine, pterygoid, and quadratojugal bones 

 have been left attached). 5. The mandibular or MeckeFs cartilage 

 (to which the angulosplenial and dentary have been left attached). 

 6. The cartilage-bones (exoccipitah ', pro-otics, sphtnethmoid, and mento- 

 meckelians]. 7. The columella, stapes, and fenestra ovalis. Sketch 

 from above and from below. 



Now proceed to examine the appendicular skeleton (pp. 46 52), 

 and sketch the shoulder-girdle and fore-limb, and the hip-girdle and 

 hind-limb. 



Split one of the longer limb-bones (e.g., humerus or femur) 

 longitudinally with a knife, and note the marrow-cavity in the shaft 

 (Fig. 13). Place another of the long bones in 10 per cent, hydro- 

 chloric acid for an hour or two ; wash thoroughly in water and 

 examine. 



